JP2019077036A - Low-density polishing pad - Google Patents

Abstract

To provide a low-density polishing pad used in a CMP process.SOLUTION: A polishing pad 222 for polishing a substrate has a density lower than 0.5 g/cc and includes a polishing body composed of a thermosetting polyurethane material 220 in which plural closed cells 214, 218 are dispersed. In another embodiment, the substrate-polishing pad 222 has the density lower than about 0.6 g/cc and includes the polishing body composed of the above polyurethane material 220 in which plural closed cells 214, 218 are dispersed. Plural closed cells 214, 218 have the diameter bimodal distribution having a first diameter mode including the first peak of a size distribution and a second diameter mode including the second peak of thee size distribution different from the first one.SELECTED DRAWING: Figure 2G

Description

  Embodiments of the present invention are in the field of chemical mechanical polishing (CMP), in particular in the field of low density polishing pads and methods of making low density polishing pads.

  Chemical mechanical planarization or chemical mechanical polishing, generally abbreviated as CMP, is a technique used in semiconductor manufacturing to planarize semiconductor wafers or other substrates.

  The process requires the use of abrasive and corrosive chemical slurries (generally colloids), typically with polishing pads and retaining rings larger in diameter than the wafer. The polishing pad and the wafer are pressed together by a dynamic polishing head and held by a plastic retaining ring. The dynamic polishing head rotates during polishing. This approach helps to remove material, tends to make any irregular topography even, and makes the wafer flat or flat. It may be necessary to condition the wafer for the formation of additional circuitry. For example, it may be required to place the entire surface within the depth of field of the photolithography system or to selectively remove material based on its position. Typical depth of field requirements are in the angstrom level for modern sub-50 nanometer technology nodes.

  The process of material removal is not just that of abrasive scrubbing like sanding wood. The chemicals in the slurry also react with and / or weaken the material to be removed. The abrasive accelerates this weakening process, and the polishing pad helps to wipe the reacted material off the surface. In addition to advances in slurry technology, polishing pads play an important role in increasingly complex CMP operations.

  However, the evolution of CMP pad technology requires further improvement.

  Embodiments of the present invention include low density polishing pads and methods of making low density polishing pads.

  In one embodiment, a polishing pad for polishing a substrate has a density less than 0.5 g / cc and includes a polishing body comprised of a thermosetting polyurethane material. A plurality of closed cell pores are dispersed in the thermosetting polyurethane material.

  In another embodiment, a polishing pad for polishing a substrate comprises a polishing body having a density less than approximately 0.6 g / cc and comprised of a thermosetting polyurethane material. A plurality of closed cell pores are dispersed in the thermosetting polyurethane material. The plurality of closed cell pores have a bimodal distribution of diameter having a first diameter mode with a first peak of the size distribution and a second diameter mode with a second different peak of the size distribution.

In yet another embodiment, a method of making a polishing pad comprises mixing a prepolymer and a chain extender or crosslinker with a plurality of microelements to form a mixture. Each of the plurality of microelements has an initial size. The method also heats the mixture in a mold to provide a shaped abrasive body comprised of a thermosetting polyurethane material and a plurality of closed cell pores dispersed in the thermosetting polyurethane material. Including the step of A plurality of closed cell pores are formed during the heating step by expanding each of the plurality of microelements to a final larger size.
For example, the following items are provided in the embodiment of the present invention.
(Item 1)
A polishing pad for polishing a substrate, said polishing pad comprising
An abrasive body having a density less than 0.5 g / cc, wherein
Thermosetting polyurethane material,
An abrasive body comprising: a plurality of closed cell holes dispersed in the thermosetting polyurethane material.
(Item 2)
The polishing pad according to item 1, wherein the polishing body is a homogeneous polishing body.
(Item 3)
3. The polishing pad of claim 1, wherein each of the plurality of closed cell pores comprises a physical shell comprising a material different from the thermosetting polyurethane material.
(Item 4)
4. The polishing pad of claim 3, wherein the physical shell of the first portion of the plurality of closed cell holes comprises a different material than the physical shell of the second portion of the plurality of closed cell holes.
(Item 5)
The polishing pad of claim 1, wherein each of only a portion of the plurality of closed cell pores comprises a physical shell comprising a material different than the thermosetting polyurethane material.
(Item 6)
The polishing pad according to claim 1, wherein each of the plurality of closed cell pores does not include a physical shell of a material different from the thermosetting polyurethane material.
(Item 7)
10. The polishing pad of claim 1, wherein the plurality of closed cell pores provide a total cell pore volume in the thermosetting polyurethane material in the range of approximately 55-80% of the total volume of the thermosetting polyurethane material. .
(Item 8)
The abrasive body is
A first grooved surface,
The polishing pad of claim 1, further comprising: a second flat surface opposite the first surface.
(Item 9)
The polishing pad of claim 1, wherein each of the plurality of closed cell pores is essentially spherical.
(Item 10)
The plurality of closed cell pores have a bimodal distribution of diameter having a first diameter mode with a first peak of the size distribution and a second diameter mode with a second different peak of the size distribution , The polishing pad according to item 1.
(Item 11)
11. A polishing pad according to item 10, wherein the closed cell holes of the first diameter mode each comprise a physical shell comprising a material different from the thermosetting polyurethane material.
(Item 12)
12. The polishing pad according to claim 11, wherein the closed cell holes of the second diameter mode each comprise a physical shell comprising a material different from the thermosetting polyurethane material.
(Item 13)
13. The polishing pad of claim 12, wherein the physical shell of each closed cell hole of the second diameter mode comprises a different material than the physical shell of the closed cell hole of the first diameter mode.
(Item 14)
The first peak of the size distribution of the first diameter mode has a diameter in the range of approximately 10 to 50 microns, and the second peak of the size distribution of the second diameter mode is approximately 10 to 150 microns 11. A polishing pad according to item 10, having a diameter in the range of
(Item 15)
11. A polishing pad according to item 10, wherein the first diameter mode overlaps with the second diameter mode.
(Item 16)
11. A polishing pad according to item 10, wherein the first diameter mode has essentially no overlap with the second diameter mode.
(Item 17)
11. A polishing pad according to item 10, wherein the total frequency count of the first diameter mode is not equal to the total frequency count of the second diameter mode.
(Item 18)
11. The polishing pad of item 10, wherein a total frequency count of the first diameter mode is approximately equal to a total frequency count of the second diameter mode.
(Item 19)
11. A polishing pad according to item 10, wherein the bimodal distribution of diameters is distributed essentially uniformly throughout the thermosetting polyurethane material.
(Item 20)
The polishing pad according to item 1, wherein the polishing body is a molded polishing body.
(Item 21)
The polishing pad of claim 1, wherein the polishing body further comprises an opacifying filler, which is approximately uniformly distributed throughout the polishing body.
(Item 22)
The polishing pad according to claim 1, further comprising an underlayer disposed on a back surface of the polishing body.
(Item 23)
A polishing pad according to claim 1, further comprising a detection area disposed within the back surface of the polishing body.
(Item 24)
The polishing pad according to claim 1, further comprising a subpad disposed on a back surface of the polishing body.
(Item 25)
The polishing pad of claim 1, further comprising a locally transparent (LAT) region disposed within the polishing body and covalently bonded thereto.
(Item 26)
A polishing pad for polishing a substrate,
The polishing pad is
An abrasive body having a density less than about 0.6 g / cc, wherein
Thermosetting polyurethane material,
An abrasive body comprising: a plurality of closed cell pores dispersed in the thermosetting polyurethane material;
The plurality of closed cell pores have a bimodal distribution of diameter having a first diameter mode with a first peak of the size distribution and a second diameter mode with a second different peak of the size distribution ,
Polishing pad.
(Item 27)
The polishing pad according to Item 26, wherein the polishing body is a homogeneous polishing body.
(Item 28)
27. A polishing pad according to item 26, wherein the closed cell pores of the first diameter mode each comprise a physical shell comprising a material different from the thermosetting polyurethane material.
(Item 29)
29. A polishing pad according to item 28, wherein the closed cell holes of the second diameter mode each comprise a physical shell comprising a material different from the thermosetting polyurethane material.
(Item 30)
30. The polishing pad according to claim 29, wherein the physical shell of each closed cell hole of the second diameter mode comprises a different material than the physical shell of the closed cell hole of the first diameter mode.
(Item 31)
The first peak of the size distribution of the first diameter mode has a diameter in the range of approximately 10 to 50 microns, and the second peak of the size distribution of the second diameter mode is approximately 10 to 150 microns Item 27. A polishing pad according to item 26, having a diameter in the range of
(Item 32)
27. A polishing pad according to item 26, wherein the first diameter mode overlaps with the second diameter mode.
(Item 33)
27. A polishing pad according to item 26, wherein the first diameter mode has essentially no overlap with the second diameter mode.
(Item 34)
27. A polishing pad according to item 26, wherein the total frequency count of the first diameter mode is not equal to the total frequency count of the second diameter mode.
(Item 35)
27. A polishing pad according to item 26, wherein the total frequency count of the first diameter mode is approximately equal to the total frequency count of the second diameter mode.
(Item 36)
27. A polishing pad according to item 26, wherein the bimodal distribution of diameters is distributed essentially uniformly throughout the thermosetting polyurethane material.
(Item 37)
A method of manufacturing a polishing pad, comprising
The method is
Mixing a prepolymer and a chain extender or crosslinker with a plurality of microelements to form a mixture, each of the plurality of microelements having an initial size;
Heating the mixture in a mold to provide a molded abrasive body comprising a thermosetting polyurethane material and a plurality of closed cell pores dispersed within the thermosetting polyurethane material,
The method wherein the plurality of closed cell holes are formed by the step of expanding each of the plurality of microelements to a final larger size during the heating step.
(Item 38)
38. The method of claim 37, wherein expanding each of the plurality of microelements to a final size comprises increasing the volume of each of the plurality of microelements by approximately 3 to 1000 times.
(Item 39)
38. The method of paragraph 37, wherein expanding each of the plurality of microelements to a final size comprises providing a final diameter of each of the plurality of microelements in the range of approximately 10 to 200 microns.
(Item 40)
38. The method of claim 37, wherein expanding each of the plurality of microelements to a final size comprises reducing the density of each of the plurality of microelements by approximately 3 to 1000 times.
(Item 41)
38. The method of paragraph 37, wherein expanding each of the plurality of microelements to a final size comprises forming an essentially spherical shape for each of the plurality of microelements of the final size.
(Item 42)
The step of mixing the prepolymer and the chain extender or the crosslinking agent with the plurality of microelements further comprises the step of mixing with the second plurality of microelements to form said mixture, said second plurality 38. A method according to item 37, wherein each of the microelements has a size.
(Item 43)
A method according to item 42, wherein the heating step is performed at a sufficiently low temperature such that the size of each of the second plurality of microelements is essentially the same before and after the heating step.
(Item 44)
A method according to item 43, wherein the heating step is performed at a temperature of about 100 degrees Celsius or less, and the second plurality of microelements have an expansion limit above about 130 degrees Celsius.
(Item 45)
43. A method according to item 42, wherein the second plurality of microelements have an expansion limit above the expansion limit of the plurality of microelements.
(Item 46)
46. The method of paragraph 45, wherein the expansion limit of the second plurality of microelements is greater than about 120 degrees Celsius and the expansion limit of the plurality of microelements is less than about 110 degrees Celsius.
(Item 47)
The mixture of prepolymers, the chain extender or crosslinker, and the second plurality of microelements have a viscosity and the prepolymer, the chain extender or crosslinker, the plurality of the plurality having the initial size. 43. A method according to item 42, wherein the microelements and the mixture of the second plurality of microelements have essentially the viscosity.
(Item 48)
50. The method according to item 47, wherein the viscosity is a predetermined viscosity and the relative amount of the second plurality of microelements in the mixture is selected based on the predetermined viscosity.
(Item 49)
50. A method according to item 47, wherein the plurality of microelements have little or no effect on the viscosity of the mixture.
(Item 50)
A heating step is performed on the thermosetting polyurethane material and the final size having the first diameter mode having the first peak of the size distribution dispersed in the thermosetting polyurethane material and each of the plurality of microelements The plurality of closed cell pores formed by expanding, and the plurality of second plurality having a second diameter mode dispersed in the thermosetting polyurethane material and having a second different peak of size distribution. 43. A method according to item 42, providing the shaped abrasive body comprising a second plurality of closed cell pores formed from microelements.
(Item 51)
The plurality of closed cell pores and the second plurality of closed cell pores provide a total cell volume in the thermosetting polyurethane material in the range of approximately 55-80% of the total volume of the thermosetting polyurethane material. The method according to item 50.
(Item 52)
38. The method of paragraph 37, wherein heating the mixture to provide the shaped abrasive body comprises forming an abrasive body having a density less than 0.5 g / cc.
(Item 53)
53. A method according to item 52, wherein the mixture has a density greater than 0.5 g / cc prior to the heating step.
(Item 54)
38. A method according to item 37, wherein the mixing step further comprises the step of injecting a gas into or within the prepolymer and the chain extender, or crosslinker, or a product formed therefrom.
(Item 55)
38. A method according to item 37, wherein the prepolymer is an isocyanate and the mixing step further comprises the step of adding water to the prepolymer.
(Item 56)
38. A method according to item 37, wherein mixing the prepolymer and the chain extender or crosslinking agent comprises mixing an isocyanate and an aromatic diamine compound, respectively.
(Item 57)
38. A method according to item 37, wherein the mixing step further comprises the step of adding an opacifying filler to the prepolymer and the chain extender or crosslinker to provide an opaque shaped abrasive body.
(Item 58)
38. A method according to item 37, wherein heating the mixture comprises causing a first partial cure in the mold and then further curing in an oven.
(Item 59)
38. A method according to item 37, wherein the step of heating in the mold comprises the step of forming a groove pattern on the polishing surface of the shaped abrasive body.
(Item 60)
38. A method according to item 37, wherein each of the plurality of microelements having the initial size comprises a physical shell and each of the plurality of microelements having the final size comprises an expanded physical shell.
(Item 61)
38. A method according to item 37, wherein each of the plurality of microelements having the initial size is a droplet and each of the plurality of microelements having the final size is a gas bubble.

FIG. 1A is a top view of a POLITEX polishing pad according to the prior art. FIG. 1B is a cross-sectional photograph of a POLITEX polishing pad according to the prior art. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. 2A-2G illustrate cross-sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention. FIG. 3 illustrates cross-sectional photographs at 100 × and 300 × magnification of a low density polishing pad including closed cell holes all based on porogen fillers, according to an embodiment of the present invention. FIG. 4 illustrates cross-sectional photographs at 100 × and 300 × magnification of low density polishing pads, including closed cell holes based in part on porogen fillers and in part based on gas bubbles, according to embodiments of the present invention Do. FIG. 5A illustrates a plot of frequency as a function of pore diameter for a wide unimodal distribution of pore diameters in a low density polishing pad, according to an embodiment of the present invention. FIG. 5B illustrates a plot of frequency as a function of pore diameter for a narrow unimodal distribution of pore diameters in a low density polishing pad, according to an embodiment of the present invention. FIG. 6A illustrates a cross-section of a low density polishing pad having an approximately 1: 1 bimodal distribution of closed cell holes, according to an embodiment of the present invention. FIG. 6B illustrates a plot of power as a function of pore diameter for the narrow distribution of pore diameters in the polishing pad of FIG. 6A, according to an embodiment of the present invention. FIG. 6C illustrates a plot of frequency as a function of pore diameter for a wide distribution of pore diameters in the polishing pad of FIG. 6A, according to an embodiment of the present invention. FIG. 7 illustrates an isometric side view of a polishing apparatus fitted with a low density polishing pad, according to an embodiment of the present invention.

  Low density polishing pads and methods of making the low density polishing pads are described herein. In the following description, numerous specific details are set forth, such as specific polishing pad designs and configurations, in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well known processing techniques, such as details regarding combinations of slurries and polishing pads that perform chemical mechanical planarization (CMP) of semiconductor substrates, do not unnecessarily obscure the embodiments of the present invention. Not listed. Furthermore, it should be understood that the various embodiments shown in the figures are illustrative representations and not necessarily drawn to scale.

  One or more embodiments described herein have a low density below about 0.6 grams per cubic centimeter (g / cc), more specifically, a low density below about 0.5 g / cc. Directed to the manufacture of a polishing pad having the The resulting pad may be based on a polyurethane material having closed cell pores that provide low density. Low density pads may be used, for example, as polishing pads designed for special chemical mechanical polishing (CMP) applications such as buffing polishing pads or liner / barrier removal. The polishing pad described herein may, in some embodiments, be manufactured to have a density in the range of 0.3 g / cc to 0.5 g / cc, for example, as low as approximately 0.357 g / cc. . In certain embodiments, low density pads have densities as low as 0.2 g / cc.

  In context, a typical CMP pad has a density of about 0.7 to 0.8 g / cc, generally greater than at least 0.5 g / cc. Traditionally, typical CMP buff pads have a "porous" design with large air bubbles open at the surface. In the case of POLITEX polishing pads, etc., a composite polyurethane skin is included on the support. Traditionally, buff pads are made of open-celled pores (e.g., fiber pads and "breathable" pads) and are very soft and of low density. Such pads typically have two basic problems with CMP: short lifetime and unstable performance compared to conventional closed cell polyurethane (but high density) CMP pads Associated with FIGS. 1A and 1B are photographs of a prior art POLITEX polishing pad viewed from above and in cross section, respectively. Referring to FIG. 1A, a portion 100A of a POLITEX polishing pad is shown as a scanning electron microscope (SEM) image magnified 300 ×. Referring to FIG. 1B, a portion 100B of a POLITEX polishing pad is shown as a scanning electron microscope (SEM) image magnified 100 times. Referring to both FIGS. 1A and 1B, the open cell structure of the prior art pad can be readily seen.

  More generally, one of the basic challenges is to create a closed cell polyurethane pad with high porosity and low density. Our proprietary investigation of the manufacture of low density polyurethane pads by molding or casting processes has resulted in pad formulations of increased amounts of porogens to ultimately provide closed cell pores within the pad material based on the added porogens. Simply adding into the mixture proved to be difficult. In particular, adding more porogen than a typical pad formulation can increase the viscosity of the formulation to a level at which the casting or molding process becomes unmanageable. It can be particularly difficult when including pre-expanded porogens or porogens that maintain essentially the same volume throughout the molding or casting process. According to embodiments of the present invention, unexpanded porogens or porogens that increase in volume throughout the molding or casting process are included in the pad formulation for ultimate production. However, in one such embodiment, if all final closed cell pores are produced from unexpanded porogen, the viscosity of the formulation may be too low in terms of ease of handling in casting or molding. Thus, in some embodiments, in addition to forming a formulation comprising unexpanded porogen or porogen that increases in volume throughout the molding or casting process, essentially the same volume throughout the pre-expanded porogen or molding or casting process Porogens that maintain the pH are also included to allow for viscosity control of the pad formulation.

Thus, in some embodiments, Unexpanded or Underexpanded porogen fillers (both referred to as UPF) that expand at temperatures above ambient temperature during manufacture by casting or molding It is used to create pores in the polishing pad. In one such embodiment, a large amount of UPF is included in the polyurethane forming mixture. The UPF expands during the pad casting process to create a low density pad with closed cell holes. The above approach for creating a polishing pad can have advantages over other techniques that have been used to form low density pads with open cells. For example, creating a final pad pore based solely on gas injection or entrainment may require specialized equipment, which may be accompanied by difficulties in controlling final pad density and in controlling final pore size and distribution. . As another example, creating a final pad pore based solely on in situ gas generation such as, for example, the water reaction of the isocyanate moiety (NCO) that produces CO ₂ bubbles can be used to control the pore size distribution. Difficulties can accompany it.

    In one aspect of the invention, a low density polishing pad may be manufactured in a molding process. For example, FIGS. 2A-2G illustrate cross sections of operations used to manufacture a polishing pad, according to an embodiment of the present invention.

  Referring to FIG. 2A, a mold 200 is provided. Referring to FIG. 2B, prepolymer 202 and curing agent 204 (eg, chain extender or crosslinker) are mixed with the plurality of microelements to form a mixture. In some embodiments, the plurality of microelements is a plurality of porogens 206, such as solid or hollow microspheres. In another embodiment, the plurality of microelements is a plurality of gas bubbles or droplets or both 208. In another embodiment, the plurality of microelements is a combination of a plurality of porogens 206 and a plurality of gas bubbles and / or droplets 208.

  Referring to FIG. 2C, the resulting mixture 210 from FIG. 2B is shown at the bottom of the mold 200. The mixture 210 includes a first plurality of microelements 212, each of the first plurality of microelements having an initial size. A second plurality of microelements 214 may also be included in the mixture 210, as described in detail below.

  Referring to FIG. 2D, the lid 216 of the mold 200 is brought together with the bottom of the mold 200, and the mixture 210 takes the form of the mold 200. In one embodiment, the mold 200 is degassed at or between the lid 216 and the bottom of the mold 200 so that no voids or voids occur in the mold 210. It is to be understood that the embodiments described herein that describe demolding the mold lid need only to bring the lid and the bottom of the mold together. That is, in some embodiments, the bottom of the mold is lifted towards the lid of the mold, while in other embodiments the lid of the mold is lifted at the same time as the bottom is lifted towards the lid , Down to the bottom of the mold.

  Referring to FIG. 2E, mixture 210 is heated in mold 200. Each of the plurality of microelements 212 is expanded to a final larger size 218 during heating. Additionally, with reference to FIG. 2F, heating cures the mixture 210 to provide a partially or fully cured pad material 220 that surrounds the microelements 218 and, if present, the microelements 214. It is used to In one such embodiment, curing forms a crosslinked matrix based on the materials of prepolymer and curing agent.

  Referring collectively to FIGS. 2E and 2F, it should be understood that the order of expanding the microelements 212 to a final larger size 218 and curing the mixture 210 is not necessarily the order shown. In another embodiment, during the heating step, the curing step of the mixture 210 occurs prior to the expansion step to the final larger size 218 of the microelements 212. In another embodiment, during the heating step, the curing step of the mixture 210 occurs simultaneously with the expansion step of the microelements 212 to a final larger size 218. In yet another embodiment, two separate heating operations are performed to cure the mixture 210 and expand the microelements 212 to a final larger size 218, respectively.

  Referring to FIG. 2G, in one embodiment, the process described above is used to provide a low density polishing pad 220. The low density polishing pad 222 is comprised of a hardened material 220 and includes expanded microelements 218 along with additional microelements 214 in an embodiment. In one embodiment, the low density polishing pad 222 is comprised of a thermosetting polyurethane material, and the expanded microelements 218 provide a plurality of closed cell pores dispersed within the thermosetting polyurethane material. Referring again to FIG. 2G, the lower portion of the figure is a plan view of the top cross section taken along the a-a 'axis. As seen in the plan view, in one embodiment, the low density polishing pad 222 has a polishing surface 228 having a groove pattern therein. In one particular embodiment as shown, the groove pattern includes radial grooves 226 and concentric grooves 228.

  Referring again to FIGS. 2D and 2E, in one embodiment, each of the plurality of microelements 212 is expanded to a final size 218 by increasing the volume of each of the plurality of microelements by approximately 3 to 1000 times. Ru. In one embodiment, each of the plurality of microelements 212 is expanded to a final size 214 such that the final diameter of each of the plurality of microelements 218 is approximately 10-200 microns. In one embodiment, each of the plurality of microelements 212 is expanded to a final size 218 by reducing the density of each of the plurality of microelements 212 by approximately 3 to 1000 times. In one embodiment, each of the plurality of microelements 212 is expanded to the final size 218 by forming each of the plurality of microelements 218 of final size essentially spherical.

In some embodiments, the plurality of microelements 212 are additive porogens, gas bubbles, or liquid bubbles that then expand to form closed cell pores in the finished polishing pad material within the pad material formulation. In some such embodiments, the plurality of closed cell pores are a plurality of larger porogens formed by expanding a corresponding smaller porogen. For example, the term "porogen" may be used to indicate micro or nano scale spherical or nearly spherical particles having a "hollow" core. The hollow core is not filled with solid material but rather comprises a gaseous or liquid core. In some embodiments, a plurality of closed cell pores, begins as unexpanded gas-filled or liquid-filled EXPANCEL ^TM which is distributed throughout the mixture. For example, by a molding process, during the time and / or shaping the polishing pad from the mixture, gas-filled or liquid-filled EXPANCEL ^TM unexpanded will expanded state. In a specific embodiment, EXPANCEL ^TM is filled with pentane. In some embodiments, each of the plurality of closed cell pores has a diameter in the range of approximately 10 to 100 microns in its expanded state, eg, the final product. Thus, in one embodiment, each of the plurality of microelements having an initial size comprises a physical shell, and each of the plurality of microelements having a final size comprises an expanded physical shell. In another embodiment, each of the plurality of microelements 212 having an initial size is a droplet and each of the plurality of microelements 218 having a final size is a gas bubble. In yet another embodiment, the mixing step of forming mixture 210 to form a plurality of microelements 218 having a final size comprises gassing the prepolymer and chain extender or crosslinker, or products formed therefrom. It further comprises the step of injecting. In certain such embodiments, the prepolymer is an isocyanate, and the mixing step further comprises the step of adding water to the prepolymer. In any case, in some embodiments, the plurality of closed cell pores include pores that are separate from one another. It is in contrast to open cell pores which can be connected to each other through a tunnel, as in the case of pores in a common sponge.

  Referring again to FIGS. 2C-2E, in some embodiments, mixing the prepolymer 202 and the chain extender or crosslinker 204 with the plurality of microelements 212 forms a second plurality of microfine particles to form the mixture 210. It further comprises mixing with element 214. Each of the second plurality of microelements 214 has a size. In one such embodiment, the heating step described in connection with FIG. 2E is essentially as described in FIG. 2E, with the size of each of the second plurality of microelements 214 before and after heating. It takes place at a sufficiently low temperature to be the same. In certain such embodiments, the heating step is performed at a temperature of about 100 degrees Celsius or less, and the second plurality of microelements 214 has an expansion threshold greater than about 130 degrees Celsius. . In another embodiment, the second plurality of microelements 214 have an expansion limit that exceeds the expansion limit of the plurality of microelements 212. In certain such embodiments, the expansion limit of the second plurality of microelements 214 is greater than approximately 120 degrees Celsius, and the expansion limit of the plurality of microelements 212 is less than approximately 110 degrees Celsius. Thus, in one embodiment, during the heating step, microelements 212 expand to provide expanded microelements 218, while microelements 214 remain essentially unchanged.

In certain embodiments, each of the second plurality of microelements 214, the entire polishing pad (e.g., load specific as elements therein) distributed, pre expansion may be configured in a EXPANCEL ^TM which is gas-filled . That is, any significant expansion that may occur to the microelements 214 is performed prior to including them in polishing pad formation, eg, prior to inclusion in the mixture 210. In a specific embodiment, EXPANCEL ^TM was pre inflated is filled with pentane. In one embodiment, the microelements 214 provide a plurality of closed cell pores having a diameter in the range of approximately 10 to 100 microns (again shown as 214 with little or no change during the molding process). In certain embodiments, the resulting plurality of closed cell pores include pores that are distinct from one another. It is in contrast to open cell pores which can be connected to each other through a tunnel, as in the case of pores in a common sponge.

  As mentioned above, increasing the porosity by adding more porogen than a typical pad formulation can increase the viscosity of the formulation to a level where the casting or molding process becomes unmanageable. It can be particularly difficult when including pre-expanded porogens or porogens that maintain essentially the same volume throughout the molding or casting process. On the other hand, if all final closed cell pores are produced from unexpanded porogen, the viscosity of the formulation may be too low in terms of ease of handling in casting or molding. To address such situations, according to embodiments of the present invention, conceptually, the mixture of prepolymer 202, chain extender or crosslinker 204, and the second plurality of microelements 214 is viscous. On the other hand, the mixture of prepolymer 202, chain extender or crosslinker 204, a plurality of microelements 212 having an initial size, and a second plurality of microelements 214 have essentially the same viscosity. That is, the inclusion of a plurality of microelements 212 having an initial (smaller) size has little or no effect on the viscosity of the mixture. In one embodiment, therefore, the viscosity described for optimal molding conditions may be selected based on the inclusion of a second plurality of microelements having a size that remains essentially constant throughout the molding process. In such an embodiment, the viscosity is therefore a predetermined viscosity, and the relative amounts of the second plurality of microelements 214 in the mixture 210 are selected based on the predetermined viscosity. And, in some embodiments, the plurality of microelements 212 have little or no effect on the viscosity of the mixture 210.

  Referring again to FIG. 2E, in one embodiment, when two different plurality of microelements are included, each of the plurality of microelements 218 having an expanded final size expand as shown through the heating process. Each of the plurality of microelements 214 has substantially the same shape and size. However, it should be understood that each of the plurality of microelements 218 having an expanded final size need not have the same shape and / or size as each of the plurality of microelements 214. In one embodiment, as detailed below in conjunction with FIGS. 6A-6C, the abrasive body of the resulting shaped pad 222 has a first peak with a first peak of size distribution as a closed cell hole. It includes a plurality of expanded microelements 218 having a diameter mode. Included together as a closed cell pore is a second plurality of microelements 214 having a second diameter mode with a second different peak of the size distribution. In some such embodiments, the plurality of closed cell pores of microelement 218 and the second plurality of closed cell pores of microelement 214 are approximately 55 of the total volume of the thermosetting polyurethane material of low density polishing pad 222. A total pore volume in the range of -80% is provided in the thermosetting polyurethane material.

  Referring again to FIGS. 2D-2G, in an embodiment, heating the mixture 210 to provide a shaped abrasive body 222 forms an abrasive body 222 having a density less than 0.5 g / cc. including. However, in one such embodiment, mixture 210 has a density greater than 0.5 g / cc prior to the heating step. In one embodiment, prepolymer 202 is an isocyanate, chain extender or crosslinking agent 204 is an aromatic diamine compound, and polishing pad 222 is comprised of a thermosetting polyurethane material 220. In certain such embodiments, the step of forming mixture 210 includes an opacifying filler on prepolymer 202 and chain extender or crosslinker 204 to provide an opaque shaped abrasive body 222 that is ultimately opaque. It further comprises the step of adding. In certain such embodiments, the opacifying filler is, but is not limited to, boron nitride, cerium fluoride, graphite, graphite fluoride, molybdenum sulfide, niobium sulfide, talc, tantalum sulfide, tungsten disulfide, or Teflon. It is a material such as (registered trademark). In some embodiments, as briefly mentioned above, the mixture 210 is only partially cured in the mold 200 and in some embodiments is further cured in an oven after removal from the mold 220 .

  In one embodiment, the polishing pad precursor mixture 210 is used to form a shaped homogenous abrasive body 222 comprised of a thermosetting, closed cell pore polyurethane material. In one such embodiment, the polishing pad precursor mixture 210 is used to ultimately form a hard pad, and only a single type of curing agent 204 is used. In another embodiment, the polishing pad precursor mixture 210 is used to ultimately form a flexible pad, and a combination of primary and secondary curing agents (together to provide 210) is used. For example, in a specific embodiment, prepolymer 202 comprises a polyurethane precursor, the primary curing agent comprises an aromatic diamine compound, and the secondary curing agent comprises an ether binder. In certain embodiments, the polyurethane precursor is an isocyanate, the primary curing agent is an aromatic diamine, and the secondary curing agent is, but is not limited to, polytetramethylene glycol, amine functionalized glycol, or amino functional Curing agents such as polyoxypropylene. In one embodiment, the prepolymer 202, the primary curing agent, and the secondary curing agent (total 204) have an approximate molar ratio of 106 parts prepolymer, 85 parts primary curing agent, and 15 parts It has a secondary curing agent, ie provides a stoichiometry of prepolymer: curing agent ratio of approximately 1: 0.96. It is to be understood that specific properties of the polishing pad or prepolymer having different hardness values and different proportions based on the first and second curing agents may be used.

  Referring again to FIG. 2G, as described above, in an embodiment, heating the mold 200 includes forming a groove pattern in the polishing surface 224 of the shaped abrasive body 222. The groove pattern as shown includes radial grooves and concentric circumferential grooves. It should be understood that radial grooves or circumferential grooves may be omitted. Furthermore, the concentric circumferential grooves may alternatively be polygons, such as nested triangles, quadrilaterals, pentagons, hexagons and the like. Alternatively, the polishing surface may be based on protrusions instead of grooves. In addition, low density polishing pads can be manufactured without grooves in the polishing surface. In one such embodiment, the molding machine's unpatterned lid is used instead of the patterned lid. Or, alternatively, the use of the lid during shaping may be omitted. If a lid is used during molding, the mixture 210 can be heated under a pressure in the range of approximately 2 to 12 pounds per square inch.

  In one aspect, low density pads can be manufactured with closed cell holes. For example, in one embodiment, the polishing pad comprises an abrasive body having a density less than 0.6 and comprised of a thermosetting polyurethane material. The plurality of closed cell pores are dispersed in the thermosetting polyurethane material. In certain embodiments, the density is less than 0.5 g / cc. In some embodiments, the plurality of closed cell pores provide a total pore volume in the range of approximately 55-80% of the total volume of the thermosetting polyurethane material in the thermosetting polyurethane material. In one embodiment, each of the plurality of closed cell pores is essentially spherical. In certain embodiments, the abrasive body further includes a first grooved surface and a second flat surface opposite the first surface, as described in connection with FIG. 2G. In one embodiment, the abrasive is a homogeneous abrasive, as described in more detail below.

  In one exemplary embodiment, each of the plurality of closed cell pores comprises a physical shell comprised of a material different from the thermosetting polyurethane material. In such cases, closed cell pores may be created by including the porogen in the mixture to be formed into the final pad manufacture, as described above.

  In another exemplary embodiment, each of the plurality of closed cell pores comprises a physical shell comprised of a material different from the thermosetting polyurethane material. The physical shell of the first portion of the plurality of closed cell pores is comprised of a different material than the physical shell of the second portion of the plurality of closed cell holes. In such cases, closed cell pores may be created by including two (eg, expanded and unexpanded) porogens in the mixture formed for final pad manufacture, as described above.

  In another exemplary embodiment, each of only a portion of the plurality of closed cell pores comprises a physical shell composed of a different material than the thermosetting polyurethane material. In such cases, closed cell pores may be created by including both the porogen and gas bubbles or droplets in the mixture to be formed for final pad manufacture, as described above.

  In another exemplary embodiment, each of the plurality of closed cell pores does not include a physical shell of a material different from the thermosetting polyurethane material. In such cases, closed cell holes may be created by including gas bubbles or droplets, or both, in the mixture to be formed for final pad manufacture, as described above.

  FIG. 3 illustrates cross-sectional photographs at 100 × and 300 × magnification of a low density polishing pad 300 including closed cell holes all based on porogen fillers, according to an embodiment of the present invention. Referring to FIG. 3, all the pores shown are formed from porogens, so that they all contain a physical shell. Some of the pores are formed from pre-expanded Expancel porogen. Another part is formed from unexpanded Expancel porogen which is expanded during the molding process used to make the polishing pad 300. In one such embodiment, the unexpanded Expancel expands at low temperature by design. The temperature of the molding or casting process exceeds the expansion temperature, and Expancel expands rapidly during molding or casting. The density of the pad 300 is approximately 0.45, and all the pores in the pad are closed cell pores.

FIG. 4 is a cross-sectional photograph at 100 × and 300 × magnification of a low density polishing pad 400 including closed cell holes based in part on a porogen filler and in part based on gas bubbles, according to embodiments of the invention. Shown. Referring to FIG. 4, the small pores shown are formed from porogens, and thus include a physical shell. More specifically, small pores are formed from pre-expanded Expancel porogen. Large pores are formed using gas. More specifically, large pores are formed with a small amount of water and surfactant injected into the pad formulation mixture just prior to molding or casting. During the chain extension chemistry, a competitive chemistry with the NCO of the water that forms CO ₂ and forms the pores takes place. It is to be understood that the type and concentration of surfactant, together with the type and level of catalyst, control the pore size and the ratio of closed / open celled pores. The density of the pad 400 is approximately 0.37, and most of the pores in the pad are closed cell pores.

  In one aspect, the distribution of pore diameters in the polishing pad is a bell curve or unimodal distribution. For example, FIG. 5A illustrates a plot of power as a function of pore diameter for a wide unimodal distribution of pore diameters in a low density polishing pad, according to an embodiment of the present invention. Referring to plot 500A of FIG. 5A, the unimodal distribution may be relatively broad. As another example, FIG. 5B illustrates a plot of power as a function of pore diameter for a narrow unimodal distribution of pore diameters in a low density polishing pad, according to an embodiment of the present invention. Referring to plot 500B of FIG. 5B, the unimodal distribution may be narrow. In either the narrow distribution or the wide distribution, only one maximum diameter frequency is provided in the polishing pad, such as the maximum frequency at 40 microns (shown as an example).

  In another aspect, low density polishing pads may instead be manufactured with a bimodal distribution of pore diameters. As an example, FIG. 6A illustrates a cross-section of a low density polishing pad having an approximately 1: 1 bimodal distribution of closed cell pores, according to an embodiment of the present invention.

  Referring to FIG. 6A, polishing pad 600 includes a homogenous polishing body 601. The homogeneous abrasive body 601 is comprised of a thermosetting polyurethane material having a plurality of closed cell holes 602 disposed within the homogeneous abrasive body 601. The plurality of closed cell holes 602 have a multimodal distribution of diameters. In one embodiment, the multimodal distribution of diameters is a bimodal distribution of diameters including a small diameter mode 604 and a large diameter mode 606, as depicted in FIG. 6A.

  In one embodiment, the plurality of closed cell holes 602 include pores that are separate from one another, as depicted in FIG. 6A. It is in contrast to open cell pores which can be connected to each other through a tunnel, as in the case of pores in a common sponge. In one embodiment, each of the closed cell pores comprises a physical shell, such as a shell of porogen. However, in another embodiment, some or all of the closed cell pores do not include a physical shell. In one embodiment, the plurality of closed cell holes 602, and thus the multimodal distribution of diameters, is essentially uniformly and homogeneous throughout the thermosetting polyurethane material of the homogeneous abrasive body 601, as depicted in FIG. 6A. Distributed.

  In one embodiment, the bimodal distribution of pore diameters of the plurality of closed cell pores 602 is approximately 1: 1, as depicted in FIG. 6A. To better illustrate the concept, FIG. 6B illustrates a plot 620 of power as a function of pore diameter for a narrow distribution of pore diameters in the polishing pad of FIG. 6A, according to an embodiment of the present invention. FIG. 6C illustrates a plot 630 of power as a function of pore diameter for a wide distribution of pore diameters within the polishing pad of FIG. 6A, according to an embodiment of the present invention.

  6A-6C, the maximum frequency diameter value of the large diameter mode 606 is approximately twice the maximum frequency diameter value of the small diameter mode 604. For example, in one embodiment, as depicted in FIGS. 6B and 6C, the maximum frequency diameter value of the large diameter mode 606 is approximately 40 microns and the maximum frequency diameter value of the small diameter mode 604 is approximately 20. It is micron. As another example, the maximum frequency diameter value of the large diameter mode 606 is approximately 80 microns and the maximum frequency diameter value of the small diameter mode 604 is approximately 40 microns.

  Referring to plot 620 of FIG. 6B, in one embodiment, the distribution of pore diameters is narrow. In a specific embodiment, the frequency of the large diameter mode 606 has essentially no overlap with the frequency of the small diameter mode 604. However, referring to plot 630 of FIG. 6C, in another embodiment, the distribution of pore diameters is broad. In a specific embodiment, the frequency of the large diameter mode 606 overlaps with the frequency of the small diameter mode 604. It should be understood that the bimodal distribution of pore diameters need not be 1: 1, as described in connection with FIGS. 6A-6C. Also, the bimodal distribution of pore diameters need not be uniform. In another embodiment, the multimodal distribution of closed cell pore diameters is graded throughout the thermosetting polyurethane material with a gradient from the first grooved surface to the second flat surface. In one such embodiment, the multimodal distribution of sloped diameters comprises two of the diameters including a small diameter mode proximate to the first grooved surface and a large diameter mode proximate to the second flat surface. Peak distribution.

  And, in some embodiments, the low density polishing pad has a bimodal diameter having a first diameter mode with a first peak of the size distribution and a second diameter mode with a second different peak of the size distribution. It has a plurality of closed cell pores with a sex distribution. In one such embodiment, the closed cells of the first diameter mode each include a physical shell comprised of a material different from the thermosetting polyurethane material. In certain such embodiments, the closed cell pores of the second diameter mode each include a physical shell comprised of a material different than the thermosetting polyurethane material. In certain such embodiments, the physical shell of each of the closed cell holes of the second diameter mode is comprised of a material different from the material of the physical shell of the closed cell holes of the first diameter mode.

  In one embodiment, the first peak of the size distribution of the first diameter mode has a diameter in the range of approximately 10 to 50 microns and the second peak of the size distribution of the second diameter mode is approximately 10 It has a diameter in the range of ̃150 microns. In one embodiment, the first diameter mode overlaps with the second diameter mode. However, in another embodiment, the first diameter mode does not essentially overlap with the second diameter mode. In one embodiment, the total frequency count of the first diameter mode is not equal to the total frequency count of the second diameter mode. However, in another embodiment, the total frequency count of the first diameter mode is approximately equal to the total frequency count of the second diameter mode. In one embodiment, the bimodal distribution of diameters is essentially uniformly distributed throughout the thermosetting polyurethane material. However, in another embodiment, the bimodal distribution of diameters is distributed to be graded throughout the thermosetting polyurethane material.

  In certain embodiments, the low density polishing pads described herein, such as polishing pads 222, 300, or 400, or variations thereof as described above, are suitable for polishing a substrate. In one such embodiment, the polishing pad is used as a buff pad. The substrate may be one used in the semiconductor manufacturing industry, such as a silicon substrate having devices or other layers disposed thereon. However, the substrate may be, but is not limited to, a MEMS device, a reticle, or a substrate for a solar cell module. Thus, as used herein, references to "a polishing pad for polishing a substrate" are intended to encompass these related possibilities.

  The low density polishing pads described herein, such as polishing pads 222, 300, or 400, or variations thereof as described above, may be comprised of a homogenous abrasive body of a thermosetting polyurethane material. In one embodiment, the homogenous abrasive body is comprised of a thermoset, closed cell pore polyurethane material. In one embodiment, the term "homogeneous" is used to indicate that the thermosetting, closed cell pore polyurethane material is constant throughout the composition of the abrasive body. For example, in one embodiment, the term "homogeneous" excludes, for example, a polishing pad comprised of multiple layers of impregnated felts or compositions (composites) of different materials. In certain embodiments, the term "thermoset" is used to indicate an irreversibly curable polymer material, such as, for example, a precursor of a material that irreversibly changes to an infusible, insoluble polymer network upon curing. Be For example, in one embodiment, the term "thermoset" is, for example, a "thermoplastic" material or a "thermoplastic", ie, it becomes liquid when heated and very glassy when sufficiently cooled Exclude the polishing pad composed of the material consisting of the polymer returning to the state. Polishing pads made from thermosetting materials are typically made from lower molecular weight precursors that react to form a polymer in a chemical reaction, while pads made from thermoplastic materials are typical It should be noted that, as the polishing pad is formed in a physical process, it is manufactured by heating the existing polymer to cause a phase change. Polyurethane thermosetting polymers are selected for the manufacture of the polishing pads described herein based on their stable thermal and mechanical properties, resistance to chemical environments, and tendency to wear resistance. obtain.

  In one embodiment, upon conditioning and / or polishing, the homogenous abrasive body has an abrasive surface roughness in the range of approximately 1 to 5 microns root mean square. In one embodiment, upon conditioning and / or polishing, the homogenous abrasive body has an abrasive surface roughness of approximately 2.35 microns root-mean-square. In one embodiment, the homogenous abrasive body has a storage modulus in the range of approximately 30 to 120 megapascals (MPa) at 25 degrees Celsius. In another embodiment, the homogeneous abrasive has a storage modulus of less than about 30 megapascals (MPa) at 25 degrees Celsius. In one embodiment, the homogeneous abrasive has a compressibility of approximately 2.5%.

  In certain embodiments, the low density polishing pads described herein, such as polishing pad 222, 300 or 400, or variations thereof as described above, include a shaped homogenous abrasive body. The term "shaped" is used to indicate that a homogenous abrasive body has been formed in a mold, as detailed above in connection with FIGS. 2A-2G. It should be understood that in other embodiments, a casting process may be used instead to fabricate low density polishing pads as described above.

  In one embodiment, the homogeneous abrasive body is opaque. In one embodiment, the term "opaque" is used to indicate a material that allows the passage of visible light of approximately 10% or less. In certain embodiments, the homogenous abrasive body is partially or wholly attributable to the inclusion of the opacifying filler (eg, as an additional component) into the homogeneous thermosetting, closed cell polyurethane material of the homogeneous abrasive body. Are opaque. In specific embodiments, the opacifying filler is, but is not limited to, boron nitride, cerium fluoride, graphite, graphite fluoride, molybdenum sulfide, niobium sulfide, talc, tantalum sulfide, tungsten disulfide, or Teflon Materials such as trademarks).

  The size of the low density polishing pad, such as pad 222, 300, or 400, may vary depending on the application. Nevertheless, several parameters can be used to make a polishing pad that is compatible with conventional process equipment or even conventional chemical mechanical process operations. For example, according to embodiments of the present invention, the low density polishing pad has a thickness in the range of approximately 0.075 inches to 0.130 inches, such as in the range of approximately 1.9 to 3.3 millimeters. In certain embodiments, the low density polishing pad has a range of approximately 20 inches to 30.3 inches, for example, approximately 50 to 77 centimeters, and in some cases, approximately 10 inches to 42 inches, for example, approximately It has a diameter in the range of 25-107 cm.

  In another embodiment of the present invention, the low density polishing pad described herein further comprises a locally transparent (LAT) region disposed within the polishing pad. In one embodiment, the LAT region is disposed within the polishing pad and covalently coupled to the polishing pad. Examples of suitable LAT regions are those filed on Jan. 13, 2010, U.S. Patent Application Nos. 12 / 657,135, assigned to NexPlanar Corporation, and September 30, 2010, assigned to NexPlanar Corporation. No. 12 / 895,465. In alternative or additional embodiments, the low density polishing pad further includes an abrasive surface and an opening disposed in the abrasive body. The opening may, for example, receive a detection device included in the platen of the polishing tool. An adhesive sheet is disposed on the back of the abrasive body. The adhesive sheet provides an impermeable seal at the opening at the back of the abrasive body. An example of a suitable opening is described in US patent application Ser. No. 13 / 184,395, filed Jul. 15, 2011 and assigned to NexPlanar Corporation. In another embodiment, the low density polishing pad further includes, for example, a detection area used with an eddy current detection system. An example of a suitable eddy current detection area is described in US patent application Ser. No. 12 / 895,465, filed Sep. 30, 2010, assigned to NexPlanar Corporation.

  The low density polishing pad described herein, such as polishing pad 222, 300, or 400, or variations thereof as described above, may further include an underlayer disposed on the back of the polishing body. In certain such embodiments, the result is a polishing pad having a bulk or base material that is different than the material of the polishing surface. In one embodiment, the composite polishing pad comprises a base or bulk layer made of a stable, essentially incompressible inert material on which the polishing surface layer is disposed. A harder base layer can provide support and strength to keep the pad intact, while a softer polishing surface layer can reduce scratches and material properties of the polishing layer and the rest of the polishing pad Allow for the separation of Examples of suitable underlayers are described in US patent application Ser. No. 13 / 306,845, filed Nov. 29, 2011, assigned to NexPlanar Corporation.

  The low density polishing pads described herein, such as polishing pads 222, 300 or 400, or their variations as described above, may be subpads disposed on the back of the polishing body, such as conventional types known in the art of CMP. The sub pad may further be included. In certain such embodiments, the subpad is comprised of a material such as, but not limited to, foam, rubber, fibers, felt or highly porous material.

  Referring again to FIG. 2G as a basis for the description, the individual grooves of the groove pattern formed in the low density polishing pad as described herein may be about 4 to about 4 at any point on each groove. It can be 100 mils deep. In some embodiments, the grooves are about 10 to about 50 mils deep at any point on each groove. The grooves may be of uniform depth, varying depth, or any combination thereof. In some embodiments, the grooves are all of uniform depth. For example, the grooved grooves may all be of the same depth. In some embodiments, some of the grooved grooves may have a particular uniform depth, while other grooves of the same pattern may have different uniform depths. For example, the groove depth may increase with increasing distance from the center of the polishing pad. However, in some embodiments, the groove depth decreases with increasing distance from the center of the polishing pad. In some embodiments, grooves of uniform depth alternate with grooves of varying depth.

  The individual grooves of the groove pattern formed in the low density polishing pad as described herein may be about 2 to about 100 mils wide at any point on each groove. In some embodiments, the grooves are about 15 to about 50 mils wide at any point on each groove. The grooves may be of uniform width, varying width, or any combination thereof. In some embodiments, the grooves are all of uniform width. However, in some embodiments, some of the concentric grooves have a certain uniform width, while other grooves of the same pattern have different uniform widths. In some embodiments, the groove width increases with increasing distance from the center of the polishing pad. In some embodiments, the groove width decreases with increasing distance from the center of the polishing pad. In some embodiments, grooves of uniform width alternate with grooves of varying width.

  According to the dimensions of depth and width described above, the individual grooves of the groove pattern described herein may include uniform volume, varying volume, including grooves at or near the location of the opening of the polishing pad. Or any combination thereof. In some embodiments, the grooves are all of uniform volume. However, in some embodiments, the groove volume increases with increasing distance from the center of the polishing pad. In some alternative embodiments, the groove volume decreases with increasing distance from the center of the polishing pad. In some embodiments, grooves of uniform volume alternate with grooves of varying volume.

  The grooved grooves described herein may have a pitch of about 30 to about 1000 mils. In some embodiments, the grooves have a pitch of about 125 mils. For circular polishing pads, the groove pitch is measured along the radius of the circular polishing pad. For CMP belts, the groove pitch is measured from the center of the CMP belt to the edge of the CMP belt. The grooves may be of uniform pitch, varying pitch, or any combination thereof. In some embodiments, the grooves are all of uniform pitch. However, in some embodiments, the groove pitch increases with increasing distance from the center of the polishing pad. In some other embodiments, the groove pitch decreases with increasing distance from the center of the polishing pad. In some embodiments, the pitch of the grooves in one sector changes as the distance from the center of the polishing pad increases, while the pitch of the grooves in adjacent sectors remains uniform. In some embodiments, the pitch of grooves in one sector increases with increasing distance from the center of the polishing pad, while the pitch of grooves in adjacent sectors increases at a different rate. In some embodiments, the pitch of the grooves in one sector increases with increasing distance from the center of the polishing pad, while the pitch of the grooves in adjacent sectors is the distance from the center of the polishing pad It decreases with the increase. In some embodiments, grooves of uniform pitch alternate with grooves of varying pitch. In some embodiments, sectors of grooves of uniform pitch alternate with sectors of grooves of varying pitch.

  The polishing pads described herein may be suitable for use in various chemical mechanical polishing apparatuses. As an example, FIG. 7 illustrates an isometric side view of a polishing apparatus fitted with a low density polishing pad, according to an embodiment of the present invention.

  Referring to FIG. 7, the polishing apparatus 700 includes a platen 704. The top surface 702 of the platen 704 can be used to support a low density polishing pad. The platen 704 may be configured to provide spindle rotation 706 and slider swing 708. The sample carrier 710 is used, for example, to hold the semiconductor wafer 711 in place during polishing of the semiconductor wafer using a polishing pad. The sample carrier 710 is further supported by a suspension mechanism 712. A slurry supply 714 is included to supply a slurry to the surface of the polishing pad before and during polishing of the semiconductor wafer. Conditioning unit 790 may also be included, and in one embodiment, includes a diamond tip for conditioning the polishing pad.

  Thus, low density polishing pads and methods of making low density polishing pads have been disclosed. According to an embodiment of the present invention, a polishing pad for polishing a substrate comprises a polishing body having a density less than 0.5 g / cc and comprised of a thermosetting polyurethane material. A plurality of closed cell pores are dispersed in the thermosetting polyurethane material. In one embodiment, the abrasive is a homogeneous abrasive.

Claims (1)

  The invention described in the specification.